1. Field of the Invention
The present invention relates to a pre-dyeing treatment process and a dyeing process for textile products comprising highly crosslinked polyacrylic fibers. This invention also relates to a pretreated and undyed textile product and a dyed textile product obtained by these processes.
2. Prior Art
Recently, a number of functional goods with cleanliness and comfortability have been developed. Among them, particular attention is paid to a textile product in which highly crosslinked polyacrylic fibers are blended to impart antibacterial and deodorizing properties (e.g. U.S. Pat. Nos. 5,853,879 and 5,292,822).
The highly crosslinked polyacrylic fiber has a peculiar chemical structure including a carboxylate. Since this chemical structure can provide a pH buffering capacity and such functions as antibacterial and deodorizing properties, a textile product containing this type of fibers is expected to serve in a broader applications. At the same time, however, the pH control capacity renders dyeing of such textile products extremely difficult. Therefore, these textile products have been dyed in the following manners.
(1) Acid or alkali is added, in advance, to a dye solution in a sufficient amount to block the pH buffering capacity of the highly crosslinked polyacrylic fiber. Then, an item to be dyed is immersed into the acid- or alkali-added dye solution and dyed therein.
(2) Acid or alkali is appropriately added in portions to a dye solution, simultaneously with the dyeing treatment of a textile product comprising highly crosslinked polyacrylic fibers. While the acid or alkali suppresses the pH buffering capacity of the highly crosslinked polyacrylic fibers, other fibers blended in the textile product can be dyed.
In the process (1), the amount of acid or alkali should be adjusted every time the dyeing condition is altered (e.g. type of blended fibers, blending ratio, type of dyes, dye concentration, bath ratio). Eventually, dye solutions are unstable and cause dyeing spots. The hue of the resultant products is unstable, poorly reproducible, and widely different from one dyeing lot to the other.
The pH buffering capacity of the highly crosslinked polyacrylic fiber is variable depending on the type of fibers to be blended with the highly crosslinked polyacrylic fiber. Hence, in the process (2), it is complicated to add acid or alkali properly in portions and thus difficult to control the pH. Similarly, the process (2) results in dyeing spots and apparent hue unevenness, thus being unsuitable for commercial production.
As described above, it is extremely difficult to dye a textile product which comprises highly crosslinked polyacrylic fibers. Bearing this issue in mind, the present inventors have made intensive researches to find a dyeing process which can simply and constantly provide a desired dyed product, and finally reached the present invention.
The present invention provides a pre-dyeing treatment process for textile products, such as yarns, woven fabrics and knit fabrics, comprising highly crosslinked polyacrylic fibers. This process comprises a pretreatment step of immersing the textile product into an acidic solution and treating the textile product at a high temperature and an elevated pressure. The pretreatment step is conducted at a high temperature ranging from 105 to 140xc2x0 C. and an elevated pressure ranging from 1.5 to 2 atm. The pre-dyeing treatment process may further comprise the step of washing the pretreated textile product with water, and the step of drying the washed textile product.
A pretreated and undyed textile product of the present invention is obtained by the pre-dyeing treatment process as mentioned above.
The present invention also provides a dyeing process for textile products comprising highly crosslinked polyacrylic fibers. This dyeing process comprises the steps of conducting the above-mentioned pre-dyeing treatment process and thereafter conventionally dyeing fibers blended with the highly crosslinked polyacrylic fibers.
A dyed textile product of the present invention is obtained by the above dyeing process.
According to the present invention, the pH buffering capacity of the highly crosslinked polyacrylic fibers is restrained during the dyeing treatment. In the meantime, the fibers blended with the highly crosslinked polyacrylic fibers can be dyed in a stable hue. It should be noted that the highly crosslinked polyacrylic fibers have their pH buffering capacity restrained temporarily, that is, only during the dyeing treatment. After the dyeing treatment, the restrained pH buffering capacity recovers in time for the final treatment of the textile product. As a result, the finished textile product is a high-quality product dyed in a stable hue, and exhibits the properties deriving from the highly crosslinked polyacrylic fibers such as moisture absorbency, antibacterial property and deodorizing property. With the high functionality and excellent design freedom, the textile product can be utilized widely in clothing applications.
The present invention is hereinafter described in detail.
The textile products as termed in this invention include yarns, yarn combination, textiles of yarn combination, knit fabrics and nonwoven cloth in any of which highly crosslinked polyacrylic fibers are mix-spun or blended with one or more types of fibers selected from synthetic fibers such as polyester fibers, polyamide fibers and polyacrylic fibers; regenerated cellulosic fibers including wet cellulosic fibers (e.g. rayon, cupro and polynosic fibers) and dry cellulosic fibers (e.g. Tencel, Lyocell); cotton, hemp, wool, silk, etc.
These textile products are utilized in underwear, socks, gloves, muffler and the like, and also in sportswear, men""s clothes, nightwear- and bedding-related products (e.g. pajamas, futon covers, bedcovers, towels, sheets, pillow covers), curtains, seat covers, car seat covers, cushion covers, architectural decoration-related products, shoe insoles, shoe linings, etc.
In the context of the present invention, the highly crosslinked polyacrylic fiber indicates a fiber prepared from an acrylic fiber by partially hydrolyzing its nitrile group to generate an amido group and a carboxylic acid group, which in turn are partially crosslinked with hydrazines or the like. After the crosslinking treatment with hydrazines, the nitrogen content normally increases by 1.0 to 10.0% by weight. The carboxylic acid group is introduced in an amount of 1.0 to 5.0 mmol/g, whereas an amido group is introduced into the remaining portion. This fiber has a pH buffering capacity to keep the pH constantly between 7.5 and 8.0, and also possesses moisture absorbency, antibacterial property, deodorizing property and the like.
The pretreatment step comprises the steps of preparing a treatment solution for the highly crosslinked polyacrylic fiber in an acid concentration of 0.02 to 0.06 mol/l, immersing a textile product into the treatment solution, and treating the textile product in the treatment solution at 105 to 140xc2x0 C. under 1.5 to 2 atm for a period of 10 to 80 minutes.
In this pretreatment step, acids for the treatment solution include common inorganic acids and organic acids, preferably organic acids with a high buffering capacity. Typical examples of the organic acids are acetic acid, citric acid, malic acid, etc. In particular, acetic acid is desirable in terms of cost and workability.
The acid concentration of the pretreatment solution is in the range of 0.02 to 0.06 mol/l. At a concentration lower than 0.02 mol/l, Na ions in the terminal carboxyl group cannot be sufficiently substituted with hydrogen. On the contrary, when the concentration exceeds 0.06 mol/l, the effect does not improve any further.
During the pretreatment step, the temperature of the treatment solution is adjusted between 105 to 140xc2x0 C., preferably between 135 to 140xc2x0 C. When the temperature is lower than 105xc2x0 C., Na ions in the terminal carboxyl group of the highly crosslinked polyacrylic fiber cannot be sufficiently substituted with hydrogen. On the other hand, a temperature over 140xc2x0 C. causes deterioration of the highly crosslinked polyacrylic fiber, which may turn yellow or harden.
Further, the pressure applied to the pretreatment solution is in the range of 1.5 to 2 atm. At a pressure below 1.5 atm, Na ions in the terminal carboxyl group of the highly crosslinked polyacrylic fiber cannot be sufficiently substituted with hydrogen. Nevertheless, even when the pressure is raised over 2 atm, the result does not improve any further.
The treating time in the pretreatment step can be determined between 10 and 80 minutes. Less than 10 minutes, the terminal carboxylate in the highly crosslinked polyacrylic fiber cannot be substituted with hydrogen in a satisfactory and stable manner. On the other hand, it is a waste of time to continue the treatment over 80 minutes, by which time the terminal substitution reaction has finished.
The above-mentioned pretreatment step is followed by the washing step of washing the pretreated textile product with water. The washing method is not particularly limited, as far as being capable of washing away the acid deposited during the pretreatment step on the fibers that are blended with the highly crosslinked polyacrylic fibers. For example, the textile product may be dip-washed in a water bath, or washed with sprinkled water while conveyed under a shower or the like.
The washing step is followed by the drying step of drying the washed textile product. Similarly, the drying method is not particularly limited, as far as being capable of drying the textile product which has been wetted in the washing step. The drying method includes hot air drying, heat drying, solar drying and air drying, to name a few.
In the present invention, the pretreated and undyed textile product encompasses any product obtained after the pretreatment step, the washing step or the drying step.
It is important to note, however, that the pretreated and undyed textile product should be dyed immediately after the pretreatment step. Otherwise, the acid which remains deposited on the pretreated and undyed textile product deteriorates the fibers blended with the highly crosslinked polyacrylic fibers. Once the pretreated and undyed textile has gone through the washing step, where the deposited acid is washed off, it is not necessary to dye the pretreated and undyed textile product instantly. Nevertheless, the washed textile product, still in the wet state, should not be left for a long period, so as to avoid development of mold. For these reasons, if the textile product is shipped to another factory or left for a while before the dyeing treatment, it is preferable to subject the pretreated textile product to the drying step.
Any of the above pretreated and undyed textile products can be dyed in a conventional manner as applied to the fibers which are blended with the highly crosslinked polyacrylic fibers in the pretreated and undyed textile product.
In a conventional dyeing method, use can be made of common dyes and auxiliaries which have been used for the blended fibers, regardless of the presence of the highly crosslinked polyacrylic fibers. Exemplary dyeing methods are dip dyeing (resisted yarn dyeing, cheese dyeing, knit fabric dyeing, woven fabric dyeing, product dyeing), continuous dyeing, printing, transfer printing and the like.
For continuous dyeing, printing and transfer printing, it is desirable to use the pretreated and undyed textile product which is obtained after the drying step, so as to prevent the deposited acid and moisture from interfering with the dyeing treatment. In contrast, in the case of dip dyeing, there is no disadvantage in using the pretreated and undyed textile product after the pretreatment step or the washing step, because the soaping treatment is usually carried out before the dyeing treatment. As an example, Table 1 lists general dyeing conditions in dip dyeing, based on the type of fibers which are blended with the highly crosslinked polyacrylic fibers in the pretreated and undyed textile product.
As prescribed in Table 1, the pretreated and undyed textile product can be dyed into an even and stable hue, in a conventional manner selected in accordance with the type of fibers blended with the highly crosslinked polyacrylic fibers.
Any of the above traditional dyeing methods is understood to be inclusive of the soaping treatment before dyeing and the post-treatment after dyeing.
The soaping treatment may be combined with either hydrogen bleach or chlorine bleach, depending on the type of blended fibers. In one soaping treatment, for example, soaping and hydrogen bleach precede the dyeing treatment. In another case, the soaping treatment and the dyeing treatment may be repeated several times (e.g. in the order of soaping, dyeing, hydrogen bleach and dyeing). In some cases, the soaping treatment may be omitted at all.
The post-dyeing treatment is performed to remove the unexhausted dye on the surface of the textile product. The post-dyeing treatment is determined according to the type of blended fibers, because they have been dyed in different manners. To give a few examples, reduction cleaning is suitable where polyester fibers or cationic dyeable polyester fibers are blended. Neutralization and soaping are combined where cellulosic fibers or polyester/cellulose fibers are blended. Once the unexhausted dye is removed, the textile product is completed with treatments like fixation, softening finish and drying, as necessary.
In the resulting textile product, the pH buffering capacity of the highly crosslinked polyacrylic fiber is constrained during the dyeing treatment. Notably, this effect lasts only temporarily and not permanently. To be specific, the inherent properties of the highly crosslinked polyacrylic fiber are suppressed during the dyeing treatment, but recovered in the course of the post-dyeing treatment and the like. As a consequence, the final textile product is dyed fixedly, without sacrificing the moisture absorbency, antibacterial property, deodorizing property and other qualities attributable to the highly crosslinked polyacrylic fiber.
Now, the present invention is described in greater detail by way of preferred examples.
Using a knitting machine (22Gxc3x9730xe2x80x3xcfx86), single yarns (yarn count: 30), obtained by evenly mix-spinning the highly crosslinked polyacrylic fiber (15%) and a polyester (85%), were woven into a piece of knit fabric which weighed about 10 kg, 220 g/m2. This knit fabric was immersed in a jet dyeing machine, scoured at 90xc2x0 C., and washed with water. Afterwards, the fabric was dried in a dryer to give an item to be dyed.
[Pre-dyeing treatment]
Acetic acid treatment solutions were prepared at nine degrees of concentration: 0.0057 mol/l, 0.0113 mol/l, 0.0227 mol/l, 0.0340 mol/l, 0.0453 mol/l, 0.0567 mol/l, 0.0680 mol/l, 0.0907 mol/l and 0.1133 mol/l.
In a dyeing tester (MINI-COLOR, manufactured by TEXAM Co., LTD.), the item to be dyed (10 g) was placed into each of the acetic acid treatment solutions at a bath ratio of 1:20. After ten minutes of immersion, each treatment solution was heated to 60xc2x0 C. over a period of 20 minutes, at which temperature the treatment was continued for 30 minutes. Thereafter, each item to be dyed was taken out of the dyeing tester and washed with water. Thus obtained was a pretreated item to be dyed which was subjected to the pre-dyeing treatment with acetic acid.
In the course of this procedure, the pH of the pretreatment solution of each acetic acid concentration was measured in the starting bath, in the bath 10 minutes after immersion of the item to be dyed, and in the finishing bath.
The measurement values are given in Table 2 below.
Additionally, similar pretreated items to be dyed were obtained by the above pre-dyeing treatment, except for changing the treating temperature to 100xc2x0 C. and 130xc2x0 C. The pH of the pretreatment solution of each acetic acid concentration was measured in the starting bath, in the bath 10 minutes after immersion of the item, and in the finishing bath.
In the case of the 100xc2x0 C. pretreatment, the treatment solution was first heated up to 100xc2x0 C. over a period of 30 minutes. Then, each item to be dyed was treated therein for 30 minutes at 100xc2x0 C. Finally, the solution was cooled down to 80xc2x0 C. for measurement of the pH in the finishing bath.
For the 130xc2x0 C. pretreatment, the treatment solution was first heated up to 130xc2x0 C. over a period of 50 minutes. Then, each item to be dyed was treated therein for 30 minutes at 130xc2x0 C. Finally, the solution was cooled down to 80xc2x0 C. for measurement of the pH in the finishing bath.
The measurement values are given in Table 2.
[Dyeing treatment]
Each of the pretreated items to be dyed and a dye solution for polyester fibers were fed into a dyeing tester (MINI-COLOR, manufactured by TEXAM CO., LTD.) at a bath ratio of 1:20. The pretreated item was soaked in the dye solution for 10 minutes. Then, the solution was heated to 135xc2x0 C. over a period of 50 minutes, at which temperature the dyeing treatment was effected for 30 minutes. Thereafter, the dye solution was cooled slowly, and the item was washed thoroughly with water.
According to the acetic acid concentration, the pH of each dye solution was measured in the starting bath, in the bath 10 minutes after immersion of the pretreated items, and in the finishing bath where the solution was cooled down to 50xc2x0 C. after the completion of dyeing.
As the reduction treatment to be conducted after the dyeing treatment, the dyed item was put into the dyeing tester (MINI-COLOR, manufactured by TEXAM CO., LTD.) and immersed in a reduction treatment solution at a bath ratio of 1:20. After 10 minutes of immersion, the solution was heated up to 80xc2x0 C. in 10 minutes to effect the reduction treatment. Following the reduction treatment, the dyed item was placed in the dyeing tester (MINI-COLOR, manufactured by TEXAM CO., LTD.) and immersed in a softening treatment solution at a bath ratio of 1:20. After 10 minutes of immersion at an ambient temperature, a series of dyeing steps was finished with centrifugal extraction and hot air drying.
For each pretreatment solution which differed in the acetic acid concentration, the above-described dyeing treatment was repeated to dye five pretreated items. The dyed items were visually evaluated for reproducibility and uniformity of dyeing and ranked in four grades (excellent, good, fair and poor).
For the dye solution, a gray disperse dye was prepared by mixing 0.014% owf of blue disperse dye (manufactured by Sumitomo Chemical Co., Ltd.), 0.0044% owf of red disperse dye (manufactured by Sumitomo Chemical Co., Ltd.), and 0.003% owf of yellow disperse dye (manufactured by Mitsubishi Kasei Kogyo Kabushiki Kaisha). Apart from this, a one-liter solution mixture was prepared by adding 1 g/l ows of dispersing agent (IONET R-1, manufactured by Sanyo Chemical Industries, Ltd.) and 0.00453 mol/l of acetic acid. The dye solution was obtained by feeding the gray disperse dye and 200 cc of the solution mixture into the dyeing tester.
As the reduction treatment solution, a one-liter solution mixture was prepared by adding 2 g of causic soda, 2 g of hydrosulfite and 1 g of activator (detergent). In use, 200 cc of this solution mixture was fed into the dyeing tester. For the softening treatment solution, 3 g of polyethylene wax softening agent was added to give a one-liter solution mixture. Likewise, 200 cc of the solution mixture was added into the dyeing tester.
Tables 3 and 4 show the results of the pH measurement and the reproducibility/uniformity evaluation.